Gas-filled thyratron



J1me 1953 i A. o. PALMER 2,838,709

GAS-FILLED mm'raou Filed Aug. 19, 1954 INVEN TOR.

ALBERT O. PALMER GAS-FILLED THYRATRON Albert 0. Palmer, Stamford, Conn., assignor to Maclllett Laboratories, Incorporated, Springdale, Conn., a corporation of Connecticut Application August 19, 1954, Serial No. 450,913

2 Claims. (Cl. 313-246) This invention relates to a novel gas-filled electron tube of the thyratron type. More specifically, this invention relates to a novel electrode arrangement for use in such tube structures. 7

A limitation on tube geometry for hydrogen thyratrons in the prior art has been the necessity of spacing the anode and its shielding structure no further apart than several times the mean free path of gas ions at the tubes gas pressure. In order to adhere strictly to this requirement with the prior art planar anode structures of relatively disk-like form, it has been necessary to employ a relatively complex can-like structure which closely surrounds the anode.

The present invention provides a much simplified electrode structure wherein the actual grid potential member is close spaced to the anode only in the region of the active anode portion. In other regions the anode is shielded by tubular dielectric members with or without additional tubular metallic shield members of grid potential. I have found that it is unnecessary to have the grid structure surrounding the anode potential structures provided that some other shielding material such as dielectric material is provided within the critical distance from the anode support structure. In fact, use of dielectric material permits ease of fabrication and greater ease in positioning the anode structure when the dielectric material is transparent as is glass. At the same time, the grid structure may be simplified, preferably by making it a generally planar member extending directly to the vacuum envelope at every edge.

Such a simple grid structure when coupled with the use of high heat flow conductivity material is especially advantageous. The high heat flow conductance may be obtained by selection of suitable material and particularly by employing a heavy or thick walled grid structure. Thus, in the preferred embodiment of the present invention, the grid structure is a heavy walled disk which extends laterally through the vacuum envelope side walls. At its edges external of the envelope, the grid may be directly coupled to a cooling device such as a radiator.

For a better understanding of the present invention reference is made to the drawing wherein the preferred version of the present invention is shown partially in axial section and partially in elevation.

Referring to the drawing the tube structure consists of a vacuum envelope generally designated 19. This envelope preferably consists of two generally tubular glass members 11 and 12. Glass member 11 is closed at one end by reentrant portion 13 which is terminated in stem press 14.

The cathode structure, generally designated 16, is shown somewhat schematically in partial section. In the structure shown a generally tubular member 17 is mounted on lead-through conductors 18 and 19 which penetrate stem press 14. The interior of tubular member 17 is coated with oxide emitter material for producing electron emission. The end of tubular member 17 adjacent the press is closed by a lateral member (not shown). Its

' tron bombardment.

late'nted June 10, 1958 other end is partially closed by disk baflle 21 which is spaced away from cylinder 17 by angle brackets 22. Heater filament 23 is located axially within tubular mem ber 17 and has one end connected to bathe member 21 and its other end connected to lead-in conductor 19 which: is insulated from the rest of the cathode structure. Lead-- in conductor 18 is not insulated from tubular member.

1"! so that, in operation of the tube, current can flow' through lead-in conductor 18, tubularmember 17,. brackets 22, disk 21 and back through filament 23 tolead-in conductor 19.

Envelope portion 12 has a double reentrant end construction, the innermost reentrant portion being formed.

by anode structure 25. Anode structure 25 consists of a heavy anode block 26 having an active anode surface: 27 of material which is highly resistant to heat and elec-- Anode block 26 is supported by heavy walled tubular member 28 in a manner which is described more fully in my co-pending application Serial No. 438,383 filed June 22, 1954, and entitled Gas-Filled Thyratron. This heavy walled tubular member, may advantageously be composed of moderately high heat flow impedance material such as one of the iron alloys. Heavy wall tubular member 28 is, in turn, sealed to glass sealing collar 29 which is supported on reentrant neck portion 3b of the envelope end structure. Axial rod 31 serves primarily as an electrical connection to the anode structure.

The grid structure in this case is composed of a heavy Walled nickel, generally planar disk-like member 34. In the version illustrated, this wall has an axial perforation 35 through which conduction is permitted to take place. This perforation is shielded by bafile 36 spaced away from the grid structure by posts 37. Such an axial aperture is useful only up to certain current level. Current in excess of amperes must be permitted access through more than one hole in order to avoid pitting of the anode surface. Accordingly, a plurality of perforations is preferred for heavy current tubes. The perforations 39 are merely holes to permit the gas within the tube to reach all portions of the tube on both sides of the grid structure. The grid is sealed to tubular metallic envelope portions 40 and 41 and these metallic envelope portions, which are advantageously composed of glass sealing metal, are then, in turn, sealed respectively to envelope members 11 and 12.

The shape of the dielectric portion of the envelope at the end of the structure is designed so that it lies close spaced to the anode support member 28. Since the envelope portion itself is terminated at-the bottom of reentrant portion 43, a tubular dielectric member 44 is;

made to continue inwardly in close spaced relationship.

with anode support member 28. This dielectric member 44 advantageously extends into contact, or almost into. contact, with grid structure 34. The dielectric envelope.- and tubular extension 44 thus provide a shield structure: for the anode structure. Electrical flux lines are able tov accumulate Within this structure instead of extending; through the gas-filled envelope in such a way that breakdown is permitted. The presence of shielding member 44 also prevents electrical stresses which would otherwise: extend to the edge of member 41 and produce corona; or other destructive electrical effects at the glass-to-metal seal between this member and envelope member 12.

Tubular metallic shield member 45 is afiixed to the grid structure 34 and surrounds the tubular dielectricmember 44. This grid potential shield is also helpful in relieving stresses which would otherwise be concen-. trated at dielectric to metal seals in the envelope.

The preferred version of the present invention has been described. It will. be obvious to those skilled in the art that many variations within the scope of the claims:

are possible. All such variations are intended to be within the scope and spirit of the present invention.

I claim:

1. Agas-filled thyratron tube comprising a gas-tight dielectric envelope having cylindrical side walls provided with a reentrant portion at one end and having a cathode mounted in the opposite end, the reentrant portion terminating in integral coaxial tubular dielectric bifurcations, one of the bifurcations extending inwardly of the envelope substantially parallel with the side walls thereof and the other of the bifurcations being substantially the same diameter as the first bifurcation and extending coaxially outwardly of the end of the envelope and itself having a reentrant portion at its outer end, a tubular metal anode support connected at one end to the reentrant portion of the second bifurcation and carrying an anode block at its inner end, the support extending inwardly of the envelope parallel and closely spaced to the bifurcations, the anode being located within the first bifurcation closely spaced therewith and having its effective surface positioned barely within the end thereof, and a disc-like grid extending transversely of the envelope in closely spaced relation to the inner end of said first bifurcation and having its marginal portions extending through the side walls of the envelope.

2. A gas-filled thyratron tube comprising a gas-tight dielectric envelope having cylindrical side Walls provided with a reentrant portion at one end and having a cathode mounted in the opposite end, the reentrant portion terminating in integral coaxial tubular dielectric bifurcations, one of the bifurcations extending inwardly of the envelope substantially parallel with the side walls thereof and the other of the bifurcations being substantially the same diameter as the first bifurcation and extending coaxially outwardly of the end of the envelope and itself having a reentrant portion at its outer end, a tubular metal anode support connected at one end to the reentrant portion of the second bifurcation and carrying an anode block at its inner end, the support extending inwardly of the envelope parallel and closely spaced to the bifurcations, the anode being located within the first bifurcation closely spaced therewith and having its effective surface positioned barely within the end thereof, a disc-like grid extending transversely of the envelope in closely spaced relation to the inner end of said first bifurcation and having its marginal portions extending through the side walls of the envelope, and a tubular metal shield carried by and electrically connected to the grid on the side thereofnearest the anode, the shield extending coaxially of the envelope between the first bifurcation and the side walls of the envelope and closely spaced to said bifurcation.

References Cited in the file of this patent UNITED STATES PATENTS 2,284,341 Pollock May 26, 1942 2,466,059 Spencer Apr. 5, 1949 2,634,383 Gurewitsch Apr. 7, 1953 

